Northern Aplomado Falcon (Falco femoralis)

The beautiful aplomado falcon has a steel grey back, red breast, black "sash" on its belly, and striking black markings on the top of its head, around its eyes, and extending down its face.

Life History

Aplomado falcons are most often seen in pairs. They do not build their own nests, but use stick nests built by other birds. Pairs work together to find prey and flush it from cover. Aplomados eat mostly birds and insects. They are fast fliers, and often chase prey animals as they try to escape into dense grass. Parents make 25-30 hunting attempts per day in order to feed their young. Chicks are fed 6 or more times each day. They live up to 20 years in captivity. Falcons are being reintroduced in south Texas to bring back the population.

Habitat

Aplomado falcons require open grassland or savannah habitat with scattered trees or shrubs.

Distribution

In Texas, aplomado falcons are found in the South Texas and Trans-Pecos regions. Their geographical distribution extends to the southern tip of South America.

Threats and Reasons for Decline

The Northern Aplomado Falcon was
most commonly observed and collected
in its U.S. range during the
period 1870-1930. The falcon seemingly
disappeared in the U.S. after
the 1930s for reasons that largely
remain a mystery. It is noteworthy
to consider that the Aplomado Falcon
was at the northern limits of its continental
range in southeastern Arizona,
southern New Mexico, and
western and southern Texas; and,
therefore, possibly vulnerable to
small changes in habitat quality in
this region.

Severe overgrazing by domestic
livestock and resultant brush
encroachment in the Southwest,
including Texas, has been most frequently
implicated as the principal
cause for the species' decline. Direct
adverse effects of livestock grazing on
potential falcon prey species have
also been suggested as a possible
cause. However, a recent review of
the history of livestock trends and
practices and other ecological factors
in the Southwest in relation to the
decline of Aplomados suggests different
causes.

In the late-1800s, large numbers
of cattle were introduced onto Southwest
grasslands occupied by Aplomados
and their numbers remained high
through the 1920s. Decades of overstocking
had degraded desert grasslands
by the 1920s. Recognition of
this led to reductions in cattle numbers
by the late-1920s and 1930s, particularly
after passage of the Taylor
Grazing Act in 1934. However, cattle
stocking rates may have remained
comparatively high in western and
southern Texas well into the late-
1900s, since these ranges were mostly
in private ownership and not subject
to regulation by the federal act. At
least at some Arizona and New Mexico
sites where Aplomados occurred,
brush did not extensively invade into
grasslands until after the 1940s

There is some evidence from
early naturalists to support the
notion that prairie dogs greatly
expanded in the Southwest after the
introduction of large cattle herds.
Widespread and intensive grazing by
cattle may have stimulated such an
expansion, since prairie dogs require
low-stature grassland habitats.
Regardless of the cause, prairie dog
numbers and acreages occupied were
extremely high during the late-1800s
through about 1920. A U.S. government
campaign to control prairie
dogs on publicly-owned lands in Arizona
and New Mexico by use of
strychnine poison began in 1912, and
a similar state effort was initiated in
Texas in 1915. Prairie dogs were
substantially reduced through poisoning
by the 1920s, their decline
peaked in the 1930s, and they were
virtually eliminated from southeastern
Arizona and southwestern New
Mexico by the 1940s and 1950s,
respectively. This pattern of decline
was probably mirrored in western
Texas, except that prairie dogs were
never completely eradicated and some
populations have persisted there
through the present time.

Historic ranges of the blacktailed
prairie dog and the Northern
Aplomado Falcon in the Southwest, to
include western Texas (prairie dogs
never occurred during historic time
in southern Texas), matched closely.
This has led to speculation that habitat
conditions generated by prairie
dogs may have benefited Aplomado
Falcons. It is reasoned that overall
abundance, biomass, and catchability
of avian and small mammal prey
were greater inside prairie dog towns
than in the surrounding grasslands.
At least some potentially important
avian prey species, such as meadowlarks,
some plovers, Mourning
Dove, Horned Lark, and others, seem
to respond positively to grazing.
Others, like the Borrowing Owl, are
directly dependent on prairie dog
borrows and other prairie dog habitat
features for optimal nesting and rearing
of young. Insects, reptiles, birds,
and small mammals that used prairie
dog colonies were probably easier to
detect and catch by Aplomados than
in surrounding grasslands, where
herbaceous vegetation was denser
and higher. In similar ways, cattle
grazing may have provided short-term
benefits to Aplomados.

The natural coincidence of
Aplomado and prairie dog distributions
in the Southwest (outside southern
Texas) and their simultaneous
declines suggest that these events
may have been related. Prairie dogs
were eradicated by strychnine poisoning.
This method of control was nonselective
and undoubtedly killed
other wildlife in the vicinity of dog
towns. Aplomado Falcons could have
been adversely affected by feeding on
poisoned birds and mammals through
relay toxicity. Relay toxicity also
could have killed other raptors and
ravens that provided nest platforms
for Aplomados.

It appears that a majority of
historic encounters with Aplomado
Falcons and high numbers and
acreage of black-tailed prairie dogs
coincided with historically high livestock
stocking rates on Southwest
grasslands (all between 1870 and
1920). Aplomado falcons and blacktailed
prairie dogs, with overlapping
distributions, disappeared from the
Southwest landscape in the 1930s.
Although, it is clear that prairie dogs
were intentionally eradicated, causes
of the Aplomados disappearance
remain obscure. In Arizona and New
Mexico, large scale mesquite and
other shrub invasion into grasslands
appears to have occurred after the
demise of the falcon.

Other factors could have affected
the decline. Aplomado Falcons disappeared
rapidly throughout their U.S.
range, which suggest that a widespread
phenomenon such as climate
change could have been involved.
Throughout the U.S. and Mexican
range of the Northern Aplomado Falcon,
the long-term, cumulative impact
of cattle grazing to the recovery of
this subspecies probably has been
negative, since it eventually contributed
to the evident degradation of
desert and coastal grasslands. Grazing
by cattle increases the spread of
mesquite, diminishes water retention
on rangelands through soil compaction
and loss of herbaceous plant
cover, and interrupts natural fire
regimes by reducing plant fuel loads.
In southern Texas, relatively high
numbers of falcon eggs and specimens
were collected by professional
collectors during the early-1900s and
possibly contributed to the disappearance
of Aplomados in that region.
Particularly in southern Texas and
eastern Mexico, but also portions of
the Aplomado's former desert range,
large tracts of native grassland have
been converted to pasturelands and
croplands, thereby further reducing
the extent and quality of Aplomado
Falcon habitat.

The pesticides DDT and DDE
were not factors in the Alpomado's
disappearance, since they were not
introduced into the environment
until the late-1940s. Even though
these pesticides have been banned in
the U.S. for over 30 years, heavy concentrations
of DDT and DDE persists
in potential prey species in the U.S.
and northern Mexico. Furthermore,
these pesticides are still in use in
Mexico and other parts of Latin
America. In eastern Mexico, DDT and
DDE contamination has led to severe
eggshell thinning in Aplomados.
Birds and other organisms collected
over the past decade from the lower
Rio Grande, Laguna Madre, and other
southern Texas locations contained
heavy loads of PBCs, heavy metals,
and organochlorine pesticides.
Organophosphate pesticides are still
heavily used throughout the range of
the Aplomado Falcon, including in the
U.S., and remain a serious threat to
Aplomados. This group of pesticides
has been linked directly to the deaths
of thousands of songbirds, waterfowl,
and raptors in Argentina and parts of
the U.S. Other threats include direct
loss of habitat from various forms of
human development, secondary lead
poisoning through ingestion of game
birds (doves and quail), electrocution
by improperly designed electrical
transmission lines, and human disturbance
in breeding areas.

Ongoing Recovery

In 1986, the Northern Aplomado
Falcon was federally listed as endangered
in the U.S. and Mexico based
on evidence of population declines in
the U.S. and threats to reproduction
in eastern Mexico related to pesticide
contamination. Subsequently, the
northern subspecies was state-listed
as endangered in Arizona, New
Mexico, and Texas, and in 1990 a
federal recovery plan was prepared.

In the years since listing
occurred, general awareness of the
Aplomado's peril has grown, surveillance
of the falcon has increased, consideration
of and planning for
Aplomado habitat requirements on
public lands has improved; and new
research, focused on the Aplomado's
population ecology and habitat preferences
and requirements, has been
initiated. In 1992, two small, isolated
populations of Aplomados were
discovered in north-central Chihuahua,
Mexico in close proximity to
the U.S. Ongoing monitoring and
research efforts at these sites are providing
important insights into the
desert grassland ecology of this
species. Recently, another researchmanagement
effort led by U.S. departments
of Interior and Defense
characterized occupied Aplomado
Falcon habitat in northern Mexico
and then used that habitat "footprint"
to identify potentially suitable falcon
habitat in the U.S. The Turner
Endangered Species Fund also
recently funded a historical review of
land use and ecological conditions
that surrounded the Aplomado in the
Southwest at the time of its decline.

Reintroduction of captive-reared
Aplomados into the historic U.S.
range was considered an essential
step in the 1990 federal recovery
plan. As early as 1977, the Chihuahuan
Desert Institute at Alpine,
Texas had begun a captive breeding
program based on wild- captured
Aplomado breeding stock from southeastern
Mexico. In the 1980s, this
program was taken over and
expanded by The Peregrine Fund, a
private organization focused on the
worldwide conservation of birds of
prey, with support from the U.S. Fish
and Wildlife Service. An initial
release of captive-reared young was
made on the King Ranch in Kleberg
County, Texas in 1985. Additional
release sites on the Texas Gulf Coast
were evaluated between 1985 and
1987, and the release program was
then refocused to Laguna Atascosa
National Wildlife Refuge and
Matagorda Island. The first breeding
in the wild of released captive-reared
Aplomados occurred in 1995. Since
1997, over 100 captive-reared young
have been released annually along
the Texas Gulf Coast. To date, this
program has resulted in the establishment
of at least 37 Aplomado pairs
that have produced over 92 young in
the wild. In 2002, reintroductions
were expanded to desert grasslands
in western Texas with the release of
36 captive-reared young and future
releases are being planned for southern
New Mexico. The preliminary
results of the reintroduction program
look promising; ultimately, however,
its success will depend on the quality
of these environments to support
wild Aplomado Falcons over time.

How You Can Help

Aplomados can be sensitive to human
disturbance, especially during the
breeding season. Human activity,
including close or prolonged intrusion
in a bird's territory, or loud and
unusual noises, can cause nest abandonment.
Human intrusions can also
make Aplomados more susceptible to
detection and harm from potential
predators. A safe viewing distance is
200 yards or more. Suitable viewing
at this or greater distance may
require a spotting scope with 10 to
15 X or greater magnification. Birders
should always respect private
property rights in Texas regardless of
the species being pursued.

Birders should keep in mind that
Aplomados remain extremely rare in
Texas and are federally- and statelisted
as endangered. Therefore, all
reasonable and suspected sightings of
this bird should be reported immediately
to an expert birder, Texas Parks
and Wildlife Department, or the U.S.
Fish and Wildlife Service for further verification. Observations should
include a detailed description of the
bird's location, appearance, activity,
and surroundings. Verification of
sightings is extremely important in
the context of the Aplomado's
scarcity and future conservation.

Ultimately, recovery of Aplomados
in Texas will depend on the
interest and direct involvement of private
land owners since lands within
the falcon's former range are mostly
in private ownership. Texas land
holders interested in promoting Aplomado
Falcon conservation measures
should consult with experts in the
Texas Parks and Wildlife Department,
U.S. Fish and Wildlife Service, or The
Peregrine Fund for technical guidance
and other assistance. Texans can contribute
to nongame wildlife resources
conservation by supporting the Texas
Parks and Wildlife Department's "Special
Nongame and Endangered Species
Conservation Fund" and by purchases
of special nongame decals and stamps
issued by the department. A set portion
of the revenues generated by
these programs is used to purchase
endangered species habitats and to
support the publication of nongamewildlife
informational materials and
other nongame activities.

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